The present invention relates to an image pickup method and a photographing device when a 3D model is prepared in the photogrammetry.
In general, when a 3D model is prepared in the photogrammetry, orientation is performed on two pickup images of an object to be measured, and three-dimensional measurement is performed thereafter. Therefore, it is necessary to have a predetermined overlapping amount so that the orientation can be performed on the two pickup images used in the photogrammetry.
When a photographer carries a camera and takes photograph of an object to be measured while the photographer is moving, the photographer takes photograph of the object to be measured while confirming the images to be picked up through a finder. Also, in order that the photogrammetry is carried out on an image already picked up, a distance between two image pickup points is also needed. In actual photographing operation, two photographing points are set up, and photographing is performed in such manner that a predetermined overlapping amount is set on the object to be measured at each point.
On the other hand, when the photographing operation is performed under such condition that the camera is carried at both points, an optical axis of the camera is unstable, and data on the direction of the optical axis, tilting of the optical axis (i.e. pitch and yaw), and twisting (roll) of the optical axis or the like are not known. Therefore, an adequate overlapping amount is needed to perform the orientation on both images. However, in order that an adequate overlapping amount is obtained, there is no other way but to rely on intuition or a sixth sense of the photographer, and whether or not the photographing has been performed adequately can not be confirmed until the orientation is performed on the image picked up.
Therefore, the photogrammetry by using a handheld type camera requires high skill and has not always been accomplished in very efficient operation.